NCLEX Dosage calculation, problem with rounding numbers

Ok I have a problem here. I will sit for the NCLEX in 3 days. I am practicing NCLEX questions with the Kaplan Qbank. I had no problem with dosage calculation until I came up with these two questions:

First I came up with this question:

The nurse receives an order to administer phenobarbital (Luminal) gr ii PO to a 3-year-old child. The label on the multidose vial reads 160 mg/5 cc. How many cc of phenobarbital should the nurse administer? Type the correct answer into the blank.

When you do the math, the result is 3.75 cc which is what I answered. But the correct response was 3.8 cc. Si I figured OK I had to round the result.

But then I came up to this question:

The nurse dilutes a 2-g vial of cefazolin (Ancef) with 3 mL of diluent to yield a volume of 3.2 mL. How many mL should the nurse administer if the physician orders 550 mg IM? Type the correct answer in the blank.

So after doing the math I came up with the result 0.88 ml, so (because of the previous question) I rounded it up and answered 0.9 ml. But the correct response was 0.88 ml!

It doesn't make sense. Am I missing something? Is it a mistake from the Qbank? What is the rule for the NCLEX, do I have to round cc and ml or not (obviously you have to round drops), if so, when?

You may have better luck if you post this in the "NCLEX Discussion Forum."

Mar 28, '10

You are supposed to round to the 100ths place if it is less than 1.0 mL and round to the 10ths place if it is over 1.0 mL.

Hope that helps.

Mar 28, '10

I just finished my nursing math class. If you're measuring in cc/ml and the answer is less than 1, round to the nearest hundredth. If the answer is more than 1, round to the nearest tenth. And of course with gtts round to the nearest whole number.

You are supposed to round to the 100ths place if it is less than 1.0 mL and round to the 10ths place if it is over 1.0 mL.

Hope that helps.

oh OK it makes sense. thanks a lot.

Mar 28, '10

Now I just got this question:

The nurse cares for a client receiving potassium chloride 25 mEq IV piggyback. The potassium chloride is labeled 10 ml = 40 mEq. Record the number of milliliters of potassium chloride that the nurse should add to the IV solution. Type the correct answer into the blank.

The nurse cares for a client receiving potassium chloride 25 mEq IV piggyback. The potassium chloride is labeled 10 ml = 40 mEq. Record the number of milliliters of potassium chloride that the nurse should add to the IV solution. Type the correct answer into the blank.

correct response: 6.25

The result is not rounded in this example, why??

I don't know the "nursing" answer but I am always amused by the somewhat arbitrary rules of nursing math.

In the math, science and engineering courses I've taken, you rounded based on the values given (actually one order less than the given value). So if the values were in whole numbers, as is the case above, you could only round to nearest tens integer. The reason for this is that any values given are accurate only to the level they are expressed in. When you use them in a calculation, your answer can only be as precise as next largest values (tens in this case). So the "correct" response above - 6.25 ml - implies a greater precision than can be actually obtained with the values given. For 6.25 ml to be the true correct answer, the values given would have to be expressed in thousandths (1.000).

Except of course if it's a nursing calculation.

Dec 9, '11

From what I understand you don't round when it's an IV solution, because you can give .25 of liquid.

Dec 9, '11

You don't round the mL solution. If it had asked for an IV rate, then you would round to the nearest whole number.